Braking system for towed vehicles

ABSTRACT

A towed vehicle hitch tongue includes movably connected front and rear tongue members, and a fully exposed master cylinder connected at opposite ends thereof to the tongue members such that a rearward force urging the front tongue member toward the rear tongue member forces pressurized braking fluid out of a port thereof into a braking circuit configured to exert a braking force. The braking circuit prevents braking until the rearward force warrants braking, provides dampening of the brake action, allows the towed vehicle to reverse, and can provide emergency stopping and dampening of movement of the hitch tongue. Instead of using movable front and rear tongue members, sensors can detect what the towed vehicle is doing, and apply appropriate braking force in response.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefit of Canadian ApplicationSerial No. 2889117 filed Apr. 22, 2015, the contents of which areincorporated herein in its entirety for all purposes.

FIELD OF THE INVENTION

This disclosure relates to the field of towing vehicles and inparticular a braking system for towed vehicles.

BACKGROUND

Braking systems are required for towed vehicles such as trailers and thelike where the brakes of the towing vehicle are not sufficient toprovide adequate braking for the added weight of the towed vehicle.

Surge or inertial braking systems use the force exerted by the towedvehicle on the towing vehicle through the tow hitch apparatus toactivate brakes on the towed vehicle. Such surge braking systems aredisclosed for example in U.S. Pat. No. 4,889,212 to Temple, U.S. Pat.No. 7,806,240 to Walstrom, et al., and U.S. Pat. No. 8,708,112 toMaisonneuve.

Electronic braking systems for towed vehicles are also known where avariety of sensors determines when braking of the towed vehicle isrequired, and activates the towed vehicle brakes. Such electronicbraking systems are disclosed for example in U.S. Pat. No. 8,267,485 toBarlsen, et al. and U.S. Pat. No. 8,540,323 to Broch, et al.

Large agricultural air seeders typically include a product cart carryingproduct tanks that, when full of agricultural products, weigh well overtwice as much as the tractor towing the air seeder. Larger product cartsare sometimes mounted on tracks to reduce soil compaction. The productcart can be towed either behind the furrow opener implement of the airseeder, or between the furrow opener implement and the tractor, suchthat a train of towed vehicles is formed. In addition to the productcart and furrow opener, it is common to add another tank specificallyfor carrying fertilizer in its gaseous or liquid form. Braking systemsare necessary to control the train, particularly during transport whenthe equipment is rolling freely behind the tractor on inclined groundsurfaces.

A train including a product cart, furrow opener implement, and extrafertilizer tank can outweigh the towing tractor by over 1.5 times whenempty and when this heavy train is being towed at high transport speeds,it can cause control issues. Due to the heavy weight of the unloadedtrain and the high transport speeds that can be achieved, an unloadedimplement train can still be hazardous. Because of the heavy weight ofthe cart and the considerable distance between the tractor as a brakingpower source and the cart, providing effective braking for air seedersusing conventional towed vehicle braking systems is problematic.

SUMMARY OF THE INVENTION

The present disclosure provides a braking system for towed vehicles thatovercomes problems in the prior art.

In a first embodiment the present disclosure provides a towed vehicleapparatus comprising a hitch tongue for connecting a towed vehicle tothe tow hitch of a towing vehicle for movement in an operating traveldirection. The hitch tongue comprises a front tongue member with a frontend thereof configured to engage the tow hitch and a rear tongue memberattached to a front end of the towed vehicle, and the front tonguemember is telescopically connected to the rear tongue member such thatthe front tongue member is movable in the operating travel directionwith respect to the rear tongue member from a fully extended positionwhen the towing vehicle is exerting a towing force in the operatingtravel direction, to a fully retracted position. A front cylinder lugextends outward from the front tongue member and a rear cylinder lugextends outward from the rear tongue member. An extendable mastercylinder has a first end thereof connected to the front cylinder lug anda second end thereof connected to the rear cylinder lug such that arearward force urging the front tongue member toward the fully retractedposition forces pressurized braking fluid out of a pressurized fluidport of the master cylinder. A braking circuit is connected to thepressurized fluid port of the master cylinder and configured such thatpressurized braking fluid expelled from the pressurized fluid portexerts a braking force on wheels of the towed vehicle.

The towed vehicle apparatus of the present disclosure provides asmoothly functioning sliding hitch tongue that serves to operate amaster cylinder for actuating a brake cylinder for use with very largetowed vehicles with weights in excess of 50 or 60 tons. Maintenance issimplified by having the master cylinder fully exposed, and by providinga removable bushing section that facilitates bushing replacement.

In a second embodiment the present disclosure provides a braking systemfor a towed vehicle, the towed vehicle including a hitch tongue adaptedfor connection at a front end thereof to a towing vehicle. The systemcomprises an extendable master cylinder comprising a pressurized fluidport at a first end thereof and a reservoir port at a second endthereof, the master cylinder mounted in the hitch tongue such that arearward force urging the hitch tongue rearward exerts a correspondingforce on the master cylinder and forces pressurized braking fluid out ofa pressurized fluid port of the master cylinder. A brake conduitconnects the pressurized fluid port of the master cylinder to an inletof a brake cylinder, the brake cylinder operative to exert a brakingforce on wheels of the towed vehicle when pressurized braking fluidenters the inlet thereof. A first sequence valve in the brake conduit isconfigured to prevent flow through the brake conduit until pressurizedbraking fluid at the inlet thereof reaches a first pressure, and to opena path from the inlet thereof to an outlet thereof to allow brakingfluid to flow through the brake conduit when pressurized braking fluidat the inlet thereof exceeds the first pressure. A first restrictiveorifice is present in the brake conduit between the outlet of the firstsequence valve and the inlet of the brake cylinder. A reversing valve inthe brake conduit is configured such that when a reversing control is ina braking position, the reversing valve provides a path from the inletthereof to an outlet thereof such that pressurized braking fluid flowsthrough the brake conduit, and when the reversing control is in areversing position the reversing valve closes the path from the inletthereof to the outlet thereof, and provides a path from the outletthereof to a fluid reservoir such that pressurized braking fluid at theinlet of the brake cylinder is relieved to a fluid reservoir. A firstreturn conduit is connected at one end to the brake conduit between thefirst restrictive orifice and the inlet of the brake cylinder, and isconnected at an opposite end thereof to the pressurized fluid port ofthe master cylinder, and a first check valve in the first return conduitis configured to allow braking fluid flow from the inlet of the brakecylinder to the pressurized fluid port of the master cylinder, and toprevent braking fluid flow from the pressurized fluid port of the mastercylinder to the inlet of the brake cylinder. A second return conduitconnects the fluid reservoir to the pressurized fluid port of the mastercylinder, and a second check valve in the second return conduit isconfigured to allow braking fluid flow from the fluid reservoir to thepressurized fluid port of the master cylinder, and to prevent brakingfluid flow from the pressurized fluid port of the master cylinder to thefluid reservoir. A reservoir conduit connects the reservoir port of themaster cylinder to the fluid reservoir.

The braking system prevents braking during gradual slowing down of thetowing vehicle, or on shallow inclines, provides dampening of the brakeaction, and allows for the operator to reverse the towed vehicle withoutthe brakes being activated. Emergency stopping and dampening of slidingmovement of the hitch tongue are provided as well.

In a third embodiment the present disclosure provides a braking systemfor an air seeder, where the air seeder includes a towed vehicle with ahitch tongue extending forward from the towed vehicle and adapted at afront end thereof for connection to a towing vehicle. The systemcomprises a brake cylinder operative to exert a braking force on wheelsof the air seeder when pressurized braking fluid enters an inletthereof, wherein the braking force increases as a pressure of thepressurized braking fluid increases, and a pressurized braking fluidsource. A proportional valve is connected at an input thereof to thepressurized braking fluid source and connected at an output thereof tothe inlet of the brake cylinder. The proportional valve is operative toreduce an input braking fluid pressure at the input thereof to aselected output pressure at the output thereof. A sensor apparatus isoperative to detect a braking requirement for the towed vehicle, and acontrol module is operative to receive sensor information from thesensor apparatus and operative to vary the output pressure at the outputof the proportional valve in response to received sensor information toachieve the selected output pressure that causes the brake cylinder toexert the braking force that meets the braking requirement.

The braking system provides smooth braking action by sensing what thetowed vehicle is doing, and applying brake force as required inresponse. The system requires no moving parts that can be damaged bylarge forces encountered where, for example the product cart is towedbetween the tractor and the furrow opener implement.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof,preferred embodiments are provided in the accompanying detaileddescription which may be best understood in conjunction with theaccompanying diagrams where like parts in each of the several diagramsare labeled with like numbers, and where:

FIG. 1 is a schematic side view of an embodiment of the towed vehicleapparatus of the present disclosure, where the towed vehicle is aproduct cart towed at the rear end of an air seeder;

FIG. 2 is a perspective exploded view of the hitch tongue of theembodiment of FIG. 1;

FIG. 3 is a schematic sectional view of the bushing section of theembodiment of FIG. 1 with the shaft of the front tongue member insertedin the cylindrical aperture defined by the front and rear bushings;

FIG. 4 is a schematic assembled view of the hitch tongue of FIG. 2;

FIG. 5 is a side view of the hitch tongue of FIG. 2 with the fronttongue member in the fully extended position;

FIG. 6 is a side view of the hitch tongue of FIG. 2 with the fronttongue member in the fully retracted position;

FIG. 7 is a top view of the brake circuit of the embodiment of FIG. 1installed on the product cart, with tanks of the product cart removedfor illustration;

FIG. 8 is a schematic view of the braking circuit of the embodiment ofFIG. 1;

FIG. 9 is a schematic side view of an air seeder where the product cartis towed between the tractor and the furrow opener implement;

FIG. 10 is a schematic view of the control and circuits for an alternatebraking system shown in FIG. 11;

FIG. 11 is a top view of an alternate brake circuit suited for use on,and shown installed on the air seeder product cart of FIG. 9, with tanksof the product cart removed for illustration;

FIG. 12 is a schematic sectional side view of the force sensor of thebrake circuit of FIG. 11 that is operative to sense a rearward forceexerted on the hitch tongue;

FIG. 13 is a schematic perspective view of an alternate arrangement of ahitch tongue for use with the embodiment of FIG. 1 with the front tonguemember in the rearward position;

FIG. 14 is a schematic perspective view of the hitch tongue of FIG. 13with the front tongue member in the forward position;

FIG. 15 is a schematic top view of the hitch tongue of FIG. 13 with thefront tongue member in the forward position.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 schematically illustrates a common configuration of an air seeder1 where the furrow opener implement 3 is towed behind the tractor 5 andthe product cart 7 is towed behind the furrow opener implement 3.

An embodiment of a towed vehicle apparatus 10 of the present disclosureis installed on the hitch tongue 9 that connect the towed vehicle, herebeing the product cart 7, to the tow hitch 11 of a towing vehicle, herebeing the furrow opener implement 3, for movement in an operating traveldirection T. As illustrated in FIGS. 2-6, the hitch tongue 9 comprises afront tongue member 13 with a front end 15 thereof configured to engagethe tow hitch 11, and a rear tongue member 17 attached to a front end ofthe product cart 7.

In the illustrated hitch tongue 9 the front tongue member 13 istelescopically connected to the rear tongue member 17 such that thefront tongue member 13 is movable in the operating travel direction Twith respect to the rear tongue member 17 from the fully extendedposition shown in FIG. 5 when the furrow opener implement 3 is exertinga towing force TF in the operating travel direction T to a fullyretracted position shown in FIG. 6.

A front cylinder lug 19 extends outward from the front tongue member 13and a rear cylinder lug 21 extends outward from the rear tongue member17, and an extendable master cylinder 23 has a first end 23A thereofconnected to the front cylinder lug 19 and a second end 23B thereofconnected to the rear cylinder lug 21. With the telescoping arrangementof the front and rear tongue members 13, 17 a rearward force RF urgingthe front tongue member 13 toward the fully retracted position pushesthe rod 25 of the master cylinder 23 into the barrel 27 of the mastercylinder 23 and forces pressurized braking fluid out of the pressurizedfluid port 29 of the master cylinder 23.

The product cart 7 can weigh well over 100,000 pounds when full and sovery large forces are exerted on the hitch tongue 9, and the telescopingmechanism must be strong enough to resist deformation in response tothese forces. In the illustrated apparatus 10 the front tongue member 13comprises a cylindrical shaft 31 which is slidingly engaged in acylindrical aperture 33 defined in the rear tongue member 17. The reartongue member 17 has a bushing section 35 attached to the front endthereof by removable fasteners, illustrated as bolts 37. The bushingsection 35 defines the cylindrical aperture 33 with a first bushing 39Amounted at a front end of the bushing section 35 and a second bushing39B mounted at a rear end of the bushing section 35. FIG. 3schematically illustrates the shaft 31 inserted in the bushings 39.

The cylindrical shape of the shaft 31 and the corresponding holes in thebushings 39 allows for these mating parts to be machined to closetolerances to form an engagement with little lateral movement. In use ona large product cart 7 weighing perhaps 120,000 pounds when full theshaft 31 can be about 4.5 inches in diameter and the close tolerancesfacilitated by the circular shape reduce lateral movement to a minimum.

Maintenance of the apparatus 10 is facilitated by the exposed locationof the master cylinder where removal and replacement can be done simplyby removing the pins holding it in place. Similarly the rear bushing 39Bcan be easily accessed and replaced by removing the bolts 37 attachingthe bushing section 35 to the rear tongue member 17.

To define the range of telescoping travel of the front tongue member 13with respect to the rear tongue member 17 a rear bearing plate 41 isattached to the front end of the bushing section 35. The rear bearingplate 41 includes first and second rear fastener portions 41A, 41Bextending outward from opposite sides of the bushing section 35, and afront bearing plate 43 attached to a rear end of the front tongue member13 includes first and second front fastener portions 43A, 43B extendingoutward from opposite sides of the front tongue member 13. A firstfastener, illustrated as bolt 45A extends through corresponding fastenerholes 47A in the first front and rear fastener portions 41A, 43A on afirst side of the shaft 31 and a second fastener, illustrated as bolt45B extends through corresponding fastener holes 47B in the second frontand rear fastener portions 41B, 43B on a second side of the shaft 31.

The fastener bolts 45A, 45B are slidingly engaged in the fastener holes47A, 47B and include a fastener stop on each end thereof, provided bythe head of each bolt 45 and a corresponding nut 49, configured to bearagainst the bearing plates 41, 43 when the front tongue member 13 is inthe fully extended position as illustrated in FIG. 5. The front tonguemember 13 slides back freely on the bolts 45 from the fully extendedposition toward the fully retracted position of FIG. 6 in response to arearward force RF exerted thereon, such as when the towing vehicle, hereillustrated as furrow opener implement 3, slows down faster than theproduct cart 7, or when the product cart 7 is on a downward inclinepushing against the furrow opener implement 3.

The towed vehicle apparatus 10 of the present disclosure provides asmoothly functioning sliding hitch tongue 9 that serves to operate amaster cylinder for actuating a brake cylinder for use with very largetowed vehicles with weights in excess of 50 or 60 tons. Maintenance issimplified by having the master cylinder fully exposed, and by providinga removable bushing section 35 that facilitates bushing replacement.

A braking circuit 51, schematically shown on the product cart 7 in FIG.7, is connected to the pressurized fluid port 29 of the master cylinder23 and is configured such that pressurized braking fluid expelled fromthe pressurized fluid port 29 exerts a braking force on wheels 53 of theproduct cart 7. More typically it is contemplated the braking fluid usedwill be a liquid braking fluid however a gaseous fluid such as air,could be used as well. Also in larger product carts tracks are sometimesmounted on the wheels 53 to reduce soil compaction.

A braking system is schematically illustrated in FIG. 8 that is suitedfor use with the towed vehicle apparatus 10 where the towed vehicleproduct cart 7 has a hitch tongue adapted for connection at a front endthereof to a towing vehicle, and where an extendable master cylinder 23,with a pressurized fluid port 29, is mounted in the hitch tongue 9 suchthat a rearward force urging the hitch tongue 9 rearward exerts acorresponding force on the master cylinder and forces pressurizedbraking fluid out of the pressurized fluid port 29 of the mastercylinder 23.

A brake conduit 55 connects the pressurized fluid port 29 of the mastercylinder 23, on the path indicated by the arrows, to an inlet 57 of abrake cylinder 59 and the brake cylinder 59 is operative to exert abraking force on the wheels 53 of the product cart 7 when pressurizedbraking fluid enters the inlet 57.

In order to reduce undue wear on the brakes, the braking circuit 51 isconfigured such that when the rearward force RF urging the front tonguemember 13 toward the fully retracted position is less than an activationforce, no braking force is exerted on the wheels 53. For example whenthe tractor 5 and furrow opener implement 3 are slowing gradually, thereis no need for braking the cart wheels 53.

To provide this feature a first sequence valve 61 in the brake conduit55 is configured to prevent flow through the brake conduit 55 untilpressurized braking fluid at the inlet 61A of the first sequence valve61 reaches a first selected pressure, and to open a path from the inlet61A thereof to the outlet 61B of the first sequence valve 61 to allowbraking fluid to flow through the brake conduit 55 when pressurizedbraking fluid at the inlet 61A thereof exceeds the first selectedpressure. The pressure is selected to allow flow through the brakeconduit 55 when the rearward force RF, which generates the pressure,equals the activation force, which force is large enough to indicate thetractor 5 is slowing more quickly, or the product cart 7 is on a steepincline, and braking of the wheels 53 on the product cart is required.

Once the rearward force RF equals the activation force, braking fluidbegins to flow through the brake conduit 55 to the brake cylinder 59 andan initial braking force BF is exerted on the wheels 53, and as therearward force RF increases, the pressure of the braking fluid increasesand the braking force BF correspondingly increases.

The braking circuit 51 is configured to direct pressurized braking fluidthrough a first restrictive orifice 63 in the brake conduit 55 betweenthe outlet 61B of the first sequence valve 61 and the inlet 57 of thebrake cylinder 59. The first restrictive orifice 63 restricts the flowof braking fluid though the brake conduit 55 and reduces the rate ofincrease in the braking force BF to a rate that is less than a rate ofincrease in the rearward force RF. This arrangement dampens the pressurefluctuations at the brake cylinder and makes the operation of the brakessmoother.

The braking circuit 51 includes a first return conduit 65 connected atone end to the brake conduit 55 between the first restrictive orifice 63and the inlet 57 of the brake cylinder 59, and connected at an oppositeend thereof to the pressurized fluid port 29 of the master cylinder 23.A first check valve 67 in the first return conduit 65 is configured toallow braking fluid flow from the inlet 57 of the brake cylinder 59 backto the pressurized fluid port 29 of the master cylinder 23, and toprevent braking fluid flow from the pressurized fluid port 29 of themaster cylinder 23 to the inlet 57 of the brake cylinder 59.

A second return conduit 69 connects a fluid reservoir 71 to thepressurized fluid port 29 of the master cylinder 23, and a second checkvalve 73 in the second return conduit 69 is configured to allow brakingfluid flow from the fluid reservoir 71 to the pressurized fluid port 29of the master cylinder 23, and to prevent braking fluid flow from thepressurized fluid port 29 of the master cylinder 23 to the fluidreservoir 71.

The pressurized fluid port 29 is defined in the blind end of a barrel 27of the master cylinder 23, and a reservoir port 77 is defined in the rodend of the barrel 27. A reservoir conduit 75 connects the reservoir port77 of the master cylinder 23 to the fluid reservoir 71. When therearward force RF is no longer present and a towing force TF is exertedon the hitch tongue 9 the master cylinder 23 moves to the extendedposition drawing braking fluid from the brake cylinder 59 and thereservoir 71 into the blind end of the barrel 27 through the pressurizedfluid port 29 and pushing braking fluid out of the rod end of the mastercylinder 23 through the reservoir port 77. The force on the hitch tongue9 can change quickly from a rearward force RF to a significant level oftowing force TF causing braking fluid to be pushed out of the reservoirport 77 quickly and at high pressure.

To smooth the operation of the master cylinder 23, a second restrictiveorifice 79 is placed in the reservoir conduit 75 which restricts andslows flow of braking fluid out of the reservoir port 77. A third checkvalve 81 is connected to the reservoir conduit 75 in parallel with thesecond restrictive orifice 79 and is configured such that braking fluidflowing from the fluid reservoir 71 to the reservoir port 77 flowsthrough the third check valve 81, and braking fluid flowing from thereservoir port 77 to the fluid reservoir 71 is prevented from flowingthrough the third check valve 81 and must flow through the secondrestrictive orifice 81.

When the master cylinder 23 is in the extended position as seen in FIG.8, a path 83 is opened around the piston 85 to allow braking fluid toflow between the pressurized fluid port 29 and the reservoir port 77.This feature ensures there is no pressure trapped in the brake conduit55 and thus in the brake cylinder 59, when in the normally operatedtowing position.

It is commonly necessary to reverse towed vehicles, such as the productcart 7. The braking circuit 51 includes a reversing valve 87 in thebrake conduit 55 configured such that when a reversing control 89,typically located at the operator's station on the tractor 5, is in abraking position, the reversing valve 87 provides a path from the inlet87A thereof to the outlet 87B thereof such that pressurized brakingfluid flows through the brake conduit 55 to the brake cylinder 59. Whenthe reversing control 89 is in a reversing position the reversing valve87 closes the path from the inlet 87A thereof to the outlet 87B thereof,preventing braking fluid from passing to the brake cylinder 59, andprovides a path from the outlet 87B to a relief port 87C connected tothe fluid reservoir 71 such that pressurized braking fluid at the inlet57 of the brake cylinder 59 is relieved to the fluid reservoir 71 andnegligible pressure is present in any brake fluid in the brake cylinder59. Braking fluid forced out of the pressurized fluid port 29 when therearward force RF is exerted to reverse the product cart 7, thus isblocked and does not get through to the brake cylinder 59.

When the reversing control 89 is in the reversing position the reversingvalve 87 may also provide a path from the inlet 87A to the relief port87C such that any pressurized braking fluid from the pressurized port 29of the master cylinder 23 will also be diverted to the fluid reservoir71. Thus there is no appreciable pressure present in the brake conduit55.

In an emergency stopping situation, when the rearward force RF isgreater than an emergency stopping force, an emergency valve opensallowing the braking fluid to bypass the first restrictive orifice 63such that an emergency braking force is exerted substantiallyimmediately on the wheels 53. The emergency valve is provided by asecond sequence valve 91 in the brake conduit 55 configured to open apath from an inlet 91A thereof, connected to the brake conduit 55between the outlet 61B of the first sequence valve 61 and the firstrestrictive orifice 63, to an outlet 91B thereof, connected to the brakeconduit 55 between the first restrictive orifice 63 and the inlet 57 ofthe brake cylinder 59 when pressurized braking fluid at the inlet 91Athereof exceeds a second pressure emergency pressure that is greaterthan the first selected pressure which opens the first sequence valve61. For example in one configuration the first pressure can be 700pounds per square inch (psi) while the second pressure can be 2500 psi.The first and second pressure will be selected to suit the particularconfiguration of the towed vehicle apparatus 10. The valves andrestrictive orifices can be mounted in a hydraulic module 93 on frame ofthe product cart 7. The restrictive orifices can be adjusted to vary theflow restriction to achieve a desired dampening effect.

Further pressure relief valves 90 connected to the fluid reservoir 71will typically also be provided and calibrated to ensure fluid pressuresdo not exceed levels that could damage the components.

The braking system prevents braking during gradual slowing down of thetowing vehicle, or on shallow inclines, provides dampening of the brakeaction, and allows for the operator to reverse the towed vehicle withoutthe brakes being activated. Emergency stopping and dampening of slidingmovement of the hitch tongue are provided as well.

A typical air seeder includes two or three towed vehicles, typically afurrow opener implement, product tank cart, and sometimes a fertilizerwagon, in a train behind a towing tractor, each with a hitch tongueextending forward from the towed vehicle and adapted at a front endthereof for connection to a towing vehicle, and the order of thevehicles in the train can vary from one air seeder to the next.

FIG. 9 schematically illustrates a common configuration of an air seederthat includes a product cart 107 with a hitch tongue 109 extendingforward from the product cart and adapted for attachment at a front end115 thereof to a towing tractor 105, and attached at a rear end thereofto a furrow opener implement 103. In this configuration the forcesexerted on the hitch tongue 109 are considerably greater than the forcesexerted on the hitch tongue 9 described above as the hitch tongue 109carries the high draft forces required to tow the furrow openerimplement 103 along the field with the furrow openers engaged in theground. This configuration also often has a product cart with only twowheels such that considerable weight is carried by the hitch tonguebearing down on the drawbar 102 of the tractor. The sliding front andrear hitch tongue members 13 and 17 forming the hitch tongue 9 above, orany like arrangement with movable parts, would be problematic with theadded forces required in this tow between tank configuration.

FIGS. 10 and 11 schematically illustrate a braking system 110 for such atow between tank configured air seeder. The system 110 comprises a brakecylinder 159 operative to exert a braking force BF on wheels 153 of theproduct cart 107, and on wheels 153′ of the furrow opener implement 103when pressurized braking fluid enters inlets 157, 157′ of the brakecylinders 159, 159′, and wherein the braking force BF increases as apressure of the pressurized braking fluid increases. A pressurizedbraking fluid source 112 has a pressurized supply conduit 114 connectedto the input 116A of a proportional valve 116. An output 116B of theproportional valve 116 is connected to the inlets 157, 157′ of the brakecylinders 159, 159′, and a relief port 116C of the proportional valve116 is connected to a fluid reservoir, here illustrated as the returnconduit 118 of the pressurized braking fluid source 112. Theproportional valve 116 is operative to reduce an input braking fluidpressure at the input 116A thereof to a selected output pressure at theoutput 116B thereof.

The pressurized fluid source can conveniently be provided by thehydraulic system of the tractor 105. FIG. 10 schematically illustratesone suitable configuration using the tractor's hydraulic system where ahydraulic manifold 120 includes a fan valve 122, a meter valve 124, andthe proportional valve 116. The fan valve 122 connects the pressurizedsupply conduit 114 to a fan 126 and a fan return conduit 128 provides apath for braking fluid to return from the fan 126 to the return conduit118. The meter valve 124 connects the pressurized supply conduit 114 toa meter 130 and a meter return conduit 132 provides a path for brakingfluid to return from the meter 130 to the return conduit 118.

A sensor apparatus can comprise a variety of sensors and is operative todetect a braking requirement for the product cart 107, and a controlmodule 134 is operative to receive sensor information from the sensorapparatus and operative to vary the output pressure at the output 116Bof the proportional valve 116 in response to received sensor informationto achieve the selected output pressure that causes the brake cylinder159 to exert the braking force BF that meets the braking requirement.The control module 134 is also operative to open and close the fan valve122 and meter valve 124 to start or stop the fan 126 and product meter130 so that the fan and meter can be stopped during transport whileproviding pressurized braking fluid to flow through the pressurizedsupply conduit 114 to the proportional valve 116 to operate the brakes.

In the illustrated braking system 110 instead of the detecting therearward force on the hitch tongue indicating a braking requirement witha sliding tongue arrangement as described above, the sensor apparatuscan comprise, as schematically illustrated in FIG. 12, a force sensor136 between the drawbar 102 and front end of the hitch tongue 109 whichis operative to detect the braking requirement by detecting when therearward hitch force RF on the hitch tongue exceeds an activation hitchforce. The activation hitch force corresponds to the rearward force thatgenerates the first selected pressure required to open the firstsequence valve 61 in the braking circuit 51 described above, andpreventing brake activation until the rearward force reaches theactivation hitch force reduces undue wear on the brakes in the samemanner as described above.

When the rearward force RF reaches the activation hitch force thecontrol module 134 varies the output pressure at the output 116B of theproportional valve 116 to provide the output pressure that causes thebrake cylinder 159 to exert a braking force BF that maintains therearward hitch force RF on the hitch tongue 109 between the activationhitch force and a selected maximum hitch force.

Alternatively the sensor apparatus can comprise a gyroscope 138operative to sense an inclination of the product cart 107, anaccelerometer 140 operative to sense acceleration of the product cart107, and a weight sensor 142 operative to sense a weight of the productcart 107. To determine the total weight of the illustrated product cart107 the weight sensor 142 includes a first load cell 144A operative tosense a weight supported by the front end of the hitch tongue load andsecond load cells 144B in the spindles of each wheel 153 that areoperative to sense a weight supported by the wheels 153 of the productcart 107. A direct speed sensor 146, or GPS speed sensor or the like, isoperative to sense a speed of the product cart 107.

The sensor apparatus detects the braking requirement by calculating fromthe sensor information that a forward force exerted by the hitch tongue109 on the towing tractor 105 is greater than an activation hitch force.This forward force corresponds to the rearward force RF detected by theforce sensor 136, but is calculated from the sensor information ratherthan being measured directly.

Again the control module 134 varies the output pressure at the output116B of the proportional valve 116 to provide the output pressure thatcauses the brake cylinder 159 to exert a braking force BF that maintainsthe forward force exerted by the hitch tongue 109 on the towing tractor105 between the activation hitch force and a selected maximum hitchforce. In order to improve control, it is generally desirable to applybraking forces to the wheels of the last vehicle in the train, and FIG.11 schematically shows the output 116B of the proportional valve 116connected to brake cylinders 159′ of the furrow opener implement 103 toapply braking forces to the wheels 153′ thereof. Where the wheels 153′are large enough to provide sufficient braking it may be desirable thatno braking force is applied to the wheels 153 of the product cart 107,and the output 116B of the proportional valve 116 is connected only tothe brake cylinders 159′ on the furrow opener implement 103.

FIG. 11 also schematically illustrates an accumulator 95 connected tothe pressurized supply conduit 114. Pressurized fluid, liquid or air,can be stored in the accumulator under pressure to provide pressurizedfluid for braking when the pressurized braking fluid source 112 isinactive. The pressurized fluid in the accumulator 95 can be used toprovide a temporary parking brake.

The braking system 110 provides smooth braking action by sensing whatthe product cart 107 is doing, and applying brake force as required inresponse. The system 110 requires no moving parts that can be damaged bylarge forces encountered where, for example the product cart 107 istowed between the tractor 105 and the furrow opener implement 103.Braking forces can be applied to either the product cart 107 or thefurrow opener implement 103 or both.

FIGS. 13-15 schematically illustrate an alternate arrangement of a hitchtongue 209 for use with the towed vehicle apparatus 10 of the presentdisclosure. The hitch tongue 209 comprises a front tongue member 213pivotally connected to the rear tongue member 217 about a tongue pivotaxis TPA defined by pin 212 oriented substantially perpendicular to theoperating travel direction T such that a distal side 213A of the fronttongue member 213 that is distal to the tongue pivot axis TPA pivotsfrom a forward position, shown in FIG. 14, when the towing vehicle isexerting a towing force TF in the operating travel direction T, to arearward position, shown in FIG. 13, when the towing vehicle is exertinga rearward force R. The front and rear cylinder lugs 219, 221, extendoutward from the distal side 213A of the front tongue member 213 and adistal side 217A of the rear tongue member 217.

A front fastener portion 243 extends out from the front tongue member213 and a rear fastener portion 241 extends out from the rear tonguemember 217. A first fastener 245A extends through corresponding firstfastener holes 247A in the front and rear fastener portions and a secondfastener 245B extends through corresponding second fastener holes 247Bin the front and rear fastener portions 241, 243.

The first and second fasteners 245A, 245B are, like the slidingfasteners 45A, 45B described above, slidingly engaged in thecorresponding fastener holes 247A, 247B and include a fastener stop oneach end thereof, provided by the head of each bolt 245 and acorresponding nut 249, configured to bear against the fastener portions241, 243 when the front tongue member 213 is in the forward towingposition of FIG. 14. The master cylinder 223 is extended in response toa towing force TF and retracted in response to a rearward force RF.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

What is claimed is:
 1. A towed vehicle apparatus comprising: a hitchtongue for connecting a towed vehicle to a tow hitch of a towing vehiclefor movement in an operating travel direction; wherein the hitch tonguecomprises a front tongue member with a front end thereof configured toengage the tow hitch and a rear tongue member attached to a front end ofthe towed vehicle; wherein the front tongue member is movably connectedto the rear tongue member such that the front tongue member is movablein the operating travel direction with respect to the rear tongue memberfrom a forward towing position when the towing vehicle is exerting atowing force in the operating travel direction, to a rearward brakingposition; a front cylinder lug extending outward from the front tonguemember and a rear cylinder lug extending outward from the rear tonguemember; an extendable master cylinder having a first end thereofconnected to the front cylinder lug and a second end thereof connectedto the rear cylinder lug such that a rearward force urging the fronttongue member toward the fully retracted position forces pressurizedbraking fluid out of a pressurized fluid port of the master cylinder; abraking circuit connected to the pressurized fluid port of the mastercylinder and configured such that pressurized braking fluid expelledfrom the pressurized fluid port exerts a braking force on wheels of thetowed vehicle; wherein the front tongue member is telescopicallyconnected to the rear tongue member and one of the front and rear tonguemembers comprises a cylindrical shaft slidingly engaged in a cylindricalaperture defined in the other of the front and rear tongue members; andthe rear tongue member comprises a bushing section attached to a frontend thereof by removable fasteners, the bushing section defining thecylindrical aperture with a first bushing mounted at a front end of thebushing section and a second bushing mounted at a rear end of thebushing section.
 2. The apparatus of claim 1 comprising a rear bearingplate attached to the front end of the bushing section, the rear bearingplate including first and second rear fastener portions extendingoutward from opposite sides of the bushing section, and a front bearingplate attached to a rear end of the front tongue member, the frontbearing plate including first and second front fastener portionsextending outward from opposite sides of the front tongue member, and afirst fastener extending through corresponding fastener holes in thefirst front and rear fastener portions on a first side of the shaft anda second fastener extending through corresponding fastener holes in thesecond front and rear fastener portions on a second side of the shaft.3. The apparatus of claim 2 wherein the fasteners are slidingly engagedin the fastener holes and include a stop on each end thereof configuredto bear against the bearing plates when the front tongue member is inthe forward towing position.
 4. The apparatus of claim 1 wherein thebraking circuit is configured such that when the rearward force urgingthe front tongue member toward the rearward braking position is lessthan an activation force, no braking force is exerted on the wheels ofthe towed vehicle.
 5. The apparatus of claim 4 wherein the brakingcircuit is configured such that when the rearward force urging the fronttongue member toward the rearward braking position is substantiallyequal to the activation force, an initial braking force is exerted onthe wheels of the towed vehicle, and as the rearward force increases,the braking force increases.
 6. A towed vehicle apparatus comprising: ahitch tongue for connecting a towed vehicle to a tow hitch of a towingvehicle for movement in an operating travel direction; wherein the hitchtongue comprises a front tongue member with a front end thereofconfigured to engage the tow hitch and a rear tongue member attached toa front end of the towed vehicle; wherein the front tongue member ismovably connected to the rear tongue member such that the front tonguemember is movable in the operating travel direction with respect to therear tongue member from a forward towing position when the towingvehicle is exerting a towing force in the operating travel direction, toa rearward braking position; a front cylinder lug extending outward fromthe front tongue member and a rear cylinder lug extending outward fromthe rear tongue member; an extendable master cylinder having a first endthereof connected to the front cylinder lug and a second end thereofconnected to the rear cylinder lug such that a rearward force urging thefront tongue member toward the fully retracted position forcespressurized braking fluid out of a pressurized fluid port of the mastercylinder; a braking circuit connected to the pressurized fluid port ofthe master cylinder and configured such that pressurized braking fluidexpelled from the pressurized fluid port exerts a braking force onwheels of the towed vehicle; wherein the braking circuit is configuredto direct pressurized braking fluid through a restrictive orifice toreduce a rate of increase in the braking force to a rate less than arate of increase in the rearward force, and wherein when the rearwardforce is greater than an emergency stopping force, an emergency valveopens allowing the braking fluid to bypass the restrictive orifice suchthat an emergency braking force is exerted substantially immediately onthe wheels of the towed vehicle.